Synthesis of Esters of 3‐(2‐Aminoethyl)‐1H‐indole‐2‐acetic Acid and 3‐(2‐aminoethyl)‐1H‐indole‐2‐malonic acid (= 2‐[3‐(2‐aminoethyl)‐1H‐indol‐2‐yl]propanedioic acid) 4th communication on indoles, indolenines, and indolines